block

1. any interruption of the conduction of electrical impulses from the atria to the ventricles; it can occur at the level of the atria, the atrioventricular node, the bundle of His, or the Purkinje system. See heart block.

2. a type of heart block in which the blocking is at the atrioventricular junction. It is first degree when atrioventricular conduction time is prolonged; it is called second degree or partial when some but not all atrial impulses reach the ventricle; and it is called third degree or complete when no atrial impulses at all reach the ventricle, so that the atria and ventricles act independently of each other.

Bier blockregional anesthesia by intravenous injection, used for surgical procedures on the forearm or the lower leg; performed in a bloodless field maintained by a pneumatic tourniquet that also prevents anesthetic from entering the systemic circulation. Called also intravenous block and IV block.

bundle branch block (BBB) a form of heart block involving delay or failure of conduction in one of the branches in the bundle of His, as determined by an electrocardiogram. It may be complete or incomplete, transient, permanent, or intermittent, and is also named according to involvement of the left or the right bundle branch. It is impossible to determine if bundle branch block is complete or not. When associated with acute anterior wall myocardial infarction, bundle branch block identifies a high-risk patient. See accompanying table.

bundle branch block, bilateralheart block characterized by conduction disturbance in the right and left bundle branches; it may be alternate, intermittent, or permanent. Complete bilateral bundle branch block results in complete (third degree) atrioventricular block.

bundle branch block, completeheart block characterized by absence of conduction in a bundle branch or conduction delay, causing ventricular activation to occur largely or exclusively through the contralateral bundle.

bundle branch block, incompleteheart block characterized by delayed conduction within a bundle branch, resulting in a delay in activation of the ipsilateral ventricle.

bundle branch block, rightheart block characterized by a delay or failure of impulse propagation through the right bundle branch; it may be either complete or incomplete. See accompanying table.

exit blockheart block characterized by failure of an expected impulse to emerge from its focus of origin and propagate; this usually occurs with a parasystolic focus, but is also seen with sinus, junctional, and ventricular rhythms. In cardiac pacing it means that the pacemaker stimulus is not of sufficient amplitude to stimulate the heart, such as when there is a very high threshold.

fascicular blockheart block characterized by certain abnormal QRS waveforms ascribed to conduction disturbance in the anterior and posterior divisions of the left bundle branch.

fascicular block, left anteriorheart block characterized by delay or interruption of impulse conduction in the anterior superior division of the left bundle branch, resulting in asynchronous activation of the left ventricle.

fascicular block, left posteriorheart block characterized by delay or interruption of impulse conduction in the posterior inferior division of the left bundle branch, resulting in asynchronous activation of the left ventricle.

femoral blockregional anesthesia of the posterior thigh and the lower leg by injection of a local anesthetic around the femoral nerve just below the inguinal ligament at the lateral border of the fossa ovalis.

field blockregional anesthesia by blocking conduction in nerves with chemical or physical agents.

intraventricular block impaired conduction within the ventricles due to absence of conduction within the bundle branches, their ramifications, or the ventricles.

intraventricular block, unspecified any heart block characterized by an electrocardiographic pattern of intraventricular conduction disturbance and not qualifying as a bundle branch block or a fascicular block.

presacral blockregional anesthesia produced by injection of the local anesthetic into the sacral nerves on the anterior aspect of the sacrum.

pudendal blockregional anesthesia produced by blocking the pudendal nerves, accomplished by injection of the local anesthetic into the tuberosity of the ischium.

The pudendal block. The pudendal nerves can be effectively blocked by a local anesthetic, thereby anesthetizing the perineum. From Nichols and Zwelling, 1997.

retrobulbar block that performed by injection of a local anesthetic into the retrobulbar space to anesthetize and immobilize the eye.

sacral blockregional anesthesia produced by injection of the local anesthetic into the extradural space of the spinal canal.

saddle blockregional anesthesia in an area corresponding roughly with the areas of the buttocks, perineum, and inner aspects of the thighs, by introducing the anesthetic agent low in the dural sac. Called also saddle block anesthesia.

sinoatrial block a type of heart block characterized by partial or complete interference with the propagation of impulses from the sinoatrial node to the atria, resulting in delay or absence of the atrial response.

trifascicular block an imprecise term referring to heart block characterized by failure of conduction, partial or complete, in all three of the fascicles of the intraventricular conduction system; i.e., there is simultaneous right bundle branch block, left anterior hemiblock, and left posterior hemiblock. In the setting of acute anterior wall myocardial infarction, this is an ominous sign. More precise terms referring to the specifically involved structures are preferred.

vagal block (vagus nerve block) regional anesthesia produced by blocking of vagal impulses by injection of a solution of local anesthetic into the vagus nerve at its exit from the skull.

block

ankle block regional anesthesia of the foot by injection of anesthetic around the tibial nerves at the ankle.

atrioventricular block , AV block impairment of conduction of cardiac impulses from the atria to the ventricles, usually due to a block in the atrioventricular junctional tissue, and generally subclassified on the basis of severity as first, second, or third degree.

Bier block regional anesthesia by intravenous injection; used for surgical procedures on the arm below the elbow or leg below the knee that are done in a bloodless field maintained by a pneumatic tourniquet.

bifascicular block impairment of conduction in two of the three fascicles of the bundle branches.

conduction block a blockage in a nerve that prevents impulses from being conducted across a given segment although the nerve beyond is viable.

elbow block regional anesthesia of the forearm and hand by injection of local anesthetic around the median, radial, and ulnar nerves at the elbow.

entrance block in cardiology, a unidirectional impasse to conduction that prevents an impulse from entering a specific region of excitable tissue; part of the mechanism underlying parasystole.

epidural block regional anesthesia by injection into the epidural space, either between the vertebral spines, in the cervical, thoracic, or lumbar region, or into the sacral hiatus, which is also called caudal block

Production of epidural block by injection through the ligamentum flavum into the epidural space, the needle stopping just short of the dura mater.

exit block in cardiology, delay or failure of an impulse to be conducted from a specific region to surrounding tissues.

fascicular block any of a group of disorders of conduction localized within any combination of the three fascicles of the bundle branches or their ramifications.

femoral block regional anesthesia of the posterior thigh and the leg below the knee by injection of a local anesthetic around the femoral nerve just below the inguinal ligament at the lateral border of the fossa ovalis.

field block regional anesthesia by encircling the operative field with injections of a local anesthetic.

heart block impairment of conduction of an impulse in heart excitation; it is subclassified as first degree when conduction time is prolonged, second degree(partial heart b.) when some atrial impulses are not conducted, and third degree(complete heart b.) when no atrial impulses are conducted; the term and its subcategories are often used specifically for atrioventricular block.

high grade atrioventricular block second or third degree atrioventricular block.

Mobitz type II block a type of second degree atrioventricular block in which dropped beats occur periodically without previous lengthening of the P–R interval, due to a block within or below the bundle of His.

motor point block interruption of impulses, by anesthesia or destruction of the nerve, at a motor point in order to relieve spasticity.

nerve block regional anesthesia by injection of anesthetics close to the appropriate nerve.

paracervical blockregional anesthesia of the inferior hypogastric plexus and ganglia produced by injection of the local anesthetic into the lateral fornices of the vagina.

parasacral block regional anesthesia produced by injection of a local anesthetic around the sacral nerves as they emerge from the sacral foramina.

paravertebral block infiltration of anesthetic into an area near the vertebrae.

block

2. Interruption, complete or partial, permanent or temporary, of the passage of a nervous impulse.

3. Atrioventricular block.

4. Sudden cessation of speech or a thought process without an immediate observable cause, sometimes considered a consequence of repression; mental block.

v.

1. To arrest passage through; obstruct.

2. To interrupt or obstruct the functioning of a physiological process, especially by the use of drugs.

block′age(blŏk′ĭj) n.

block

Etymology: OFr, bloc

1 a disruption in the conduction of a nerve impulse. The term may apply to stoppage of nerve conduction as produced by local anesthetics, inhibition of beta receptors by beta-blocker drugs, or prevention of neuromuscular transmission by blockade of nicotinic receptors by muscle-relaxant drugs.

Molecular biologyAn ungapped, aligned motif consisting of sequence segments that are clustered to reduce multiple contributions from groups of highly similar or identical sequences.

NeurologyA mental impasse.

PathologyA paraffin-embedded portion of formalin-fixed and processed tissue, from which a “ribbon” of material is cut, placed on a glass slide and stained, which is used to to establish a histologic diagnosis.

Public healthSee Sunblock.

ResearchTreatment block. A group of patients in a clinical trial of a therapeutic modality that is “blinded” according the study’s protocol, and placed in either the treatment arm or the placebo or “gold standard” arm; each block is analysed individually at the close of the study.

Vox populiA group, quantity, section or segment that is considered as a unit for some purpose, procedure, process or action.

block

(blok)

1. To obstruct; to arrest passage through.

2. A condition in which the passage of an electric impulse is arrested, wholly or in part, temporarily or permanently.

[Fr. bloquer]

block,

n1. a mental obstacle that prohibits a patient from having favorable responses to the dental professional and suggested treatment plans. 2. the blocking of sensation like pain to an area. 3. a large amount of information.

block, data,

n a physical unit of data that can be conveniently stored by a computer on an input or output device. The block is normally composed of one or more logical records or a portion of a logical record. Synonymous with physical record.

impairment of conduction in heart excitation; often applied specifically to atrioventricular heart block. See also heart block.

inverted L-block

linear infiltration cranial and dorsal to the incision site; used for flank laparotomy in cattle and sheep.

block mating

mating of all the females in a group during a brief period, e.g. within the span of three estral cycles; a characteristic of seasonal animal farming.

metabolic block

the blocking of a biosynthetic pathway due to a genetic enzyme defect or to inhibition of an enzyme by a drug or other substance.

nerve block

regional anesthesia secured by injection of an anesthetic in close proximity to the appropriate nerve.

paracervical block

anesthesia of the inferior hypogastric plexus and ganglia produced by injection of the local anesthetic into the lateral fornices of the vagina.

parasacral block

regional anesthesia produced by injection of a local anesthetic around the sacral nerves as they emerge from the sacral foramina.

presacral block

anesthesia produced by injection of the local anesthetic into the sacral nerves on the anterior aspect of the sacrum.

ring block

regional anesthesia by the injection of local anesthetic in a complete circle around a limb of a horse, or the teat of a cow.

sacral block

anesthesia produced by injection of the local anesthetic into the extradural space of the spinal canal.

saddle block

the production of anesthesia in a region corresponding roughly with the areas of the buttocks, perineum and inner aspects of the thighs, by introducing the anesthetic agent low in the dural sac.

sinus block

sinus arrest.

vagal block, vagus nerve block

blocking of vagal impulses by injection of a solution of local anesthetic into the vagus nerve at its exit from the skull.

Patient discussion about block

Q. what does a sun block cream do? and what are a UV rays?

A. It blocks out harmful Ultra violet rays from the skin as the previous entries have related; however it can also block your ability to produce vitamin D. If you live in a northerly area or one that receives limited sunlight, its recommended to get at least 15 minutes of sun a day (this is probably best done with minimal sunblock) and according to personnal sun sensitivity. Another thing to keep in mind is that sunblock works best if applied 20 minutes before sun exposure.

Q. my son is 5 and half yrs old.he is having veezing and 75%block in one nose because of adenod.is is curable he has taken steriods for one and half yrs but with not much relief for veezing. then we switched on to ayur medicines,where he had some pigmentation at some places in his body. so again we are back to allopathy. he has one nasal steriod spray now with few other medicines. in his last test, dr, said he has adenod about 75% blcok in one nose, he has prescribed medicines for one month. he has also said that a small surgery can be done to remove adenod. i would like to know how long this surgry wil take and how much of rest he wil have to take. and if this adenod is removed, wil his other problem like veezing be cured? indira rajesh

A. it's a pretty common surgery from what i remember. most of our family has any kind of nasal problem...sinusitis..adenoids...just name it. the surgery is entering through the mouth (under full sedation) and lasering/curetting - removed. it took about a week to recover , eating soft foods..and it worked!

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